The present invention generally pertains to electronic musical instruments, such as, but not restricted to, electronic organs. The present invention is directed to improvements in certain components of an electronic musical instrument, particularly the note generators; the control logic circuits for assigning the note generators to generate output frequency signals corresponding to selected notes in accordance with the availability of the note generators; and the combination of a bass note assignment circuit and bass note generator.
An electronic musical instrument, such as an electronic organ, typically may include a keyboard having a plurality of keys for selecting predetermined musical notes in predetermined octaves; an encoder coupled to the keyboard for providing digital note address signals in response to manipulation of the keys on the keyboard; and a plurality of note generators that are responsive to the digital note address signals for respectively providing a plurality of output frequency signals corresponding to the selected musical notes in the selected octaves. In some prior art electronic musical instruments, the encoder may include a clock circuit for providing a pulsed scan clock signal; a keyswitch matrix connected to the keyboard, wherein the matrix includes columns and rows of conductors and a plurality of keyswitches, and wherein each of the keyswitches is arrayed in the matrix for connecting the conductor of a given row to the conductor of a given column in response to manipulation of a given key in the keyboard; a counter circuit connected to the clock circuit for counting the pulses in the scan clock signal; a decoder connected to the rows of the keyswitch matrix and to the counter circuit for sequentially providing signal pulses on the rows of the keyswitch matrix; a multiplexer connected to the columns of the keyswitch matrix and to the first counter for scanning the columns of the keyswitch matrix at the rate of the scan clock signal and for providing a serial keyboard data signal including pulses provided from the keyboard matrix in response to manipulation of the keys, wherein each pulse in the serial keyboard data signal corresponds to a selected musical note in a selected octave; and a control logic circuit that is responsive to the serial keyboard data signal for enabling the note generators to respond to the digital scan address signals in accordance with the availability of the note generators.
The electronic musical instruments described in U.S. Pat. Nos. 3,610,799 to Watson; 3,842,702 to Tsundoo; 3,929,051 to Moore; and 3,986,423 to Rossum include typical prior art note generators and control logic circuits for assigning note generators. However, such components are complex. Accordingly, it is an object of the present invention to provide an improved electronic musical instrument wherein these components are less complex.
Electronic musical instruments typically include one set of note generators that are dedicated to generating output frequency signals corresponding to melody and harmony notes and a separate set of note generators that are dedicated to generating chord notes.
Typically, there also is included a bass note generator which generates an output frequency signal corresponding to a predetermined bass note. The bass note has a predetermined relationship to one of the chord notes and typically is selected to be one octave lower than the root note when the instrument is being operated in an automatic chord mode, or to be one octave lower than the low chord note when the instrument is being operated in a manual chord mode. When the instrument is also being operated in an rhythm mode a second bass note is also selected. In the automatic chord mode, the second bass note is selected to be one octave lower than the fifth note of the chord, and in the manual chord mode, the bass note is selected to be one octave lower than the high note of the chord.
In such a prior art system, the bass note generators have a dedicated relationship to the chord note generators related to the position of the chord note in the chord, and ROM's (read only memories) are included to provide bass note assignment signals to the base note generators that are dedicated to provide an output frequency signal corresponding to the bass note having the desired relationship to the notes in the selected chord. In addition to including a complex switching circuit, this prior art system for generating bass notes, also provides a discontinuity in the bass note waveform when a switch is made between chords having some notes in common, and the same bass note is sounded in both chords. It is an object of the present invention to provide a less complex system of bass note assignment and generation.